Mechanical properties and deformation mechanism of lightweight Al0.5NbTi3VZr0.5 high-entropy alloy via laser surface melting process

Abstract

The lightweight refractory high-entropy alloys (LRHEAs) are considered as next-generation high-performance weaponry matrix material. In this work, we employ the laser surface melting (LSM) method to ulteriorly optimize surface mechanical properties of Al_0.5NbTi₃VZr_0.5 matrix HEA, where the phase structures, mechanical properties and deformation mechanism of as-cast and LSM-treated HEAs have been investigated. The LSM process eliminates tanglesome intermetallic Zr₅Al₃ structures and effectively improves the mechanical properties of as-cast HEA. The sample after 2000 W LSM treatment exhibits the superior comprehensive mechanical properties, its tensile elongation, microhardness of remelt zone and volume wear loss are 31.6%, HV 809.6 and 296.4 × 10⁻³ mm³, representing the advancement of 85.9%, 180.1% and 64.6% compared to that of as-cast HEA sample, respectively. Additionally, the deformation behavior of the as-cast sample involves solid phase transformation, stacking faults and deformation twinnings. The deformation mechanism of as-cast Al_0.5NbTi₃VZr_0.5 HEA is transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP), the classical Burgers mechanism of BCC → HCP solid phase transformation is revealed, which obeys [111]_BCC ∥ [1120]_HCP. As for the 2000 W treated sample, the deformation mechanism is mainly TWIP as the stacking fault energy enhancement evidenced by the presence of cross-slip dislocations after LSM process.